Trypanosoma cruzi, the protozoan parasite that causes human Chagas' disease, is an obligate intracellular pathogen that lives and divides in the cytoplasm of its mammalian host cell. Despite its importance in tissue infection, persistence and disease, little is currently known about the biology of the intracellular amastigote stage of T cruzi. In particular, the essential contributions of the host cell toward the support of intracelluar replication and survival of T. cruzi remain largely unknown. With a view to identifying critical hot cell regulators of intracellular T. cruzi infection, my laboratory has established and conducted a high-throughput genome-wide functional screen to identify host cell pathways/processes that function as regulators of intracellular parasite growth. Host cell fatty acid metabolism emerged in this screen as a major pathway regulating growth of intracellular T. cruzi amastigotes in HeLa cells. We also made the observation that intracellular T. cruzi amastigotes sequester host cell glycogen, where glycogen particles are highly enriched in the vicinity of the cytosolic amastigotes. These novel findings are strongly suggestive of the ability of T. cruzi to modulate host metabolic functions in infected host cells. In support of this hypothesis, PDK4, the main regulator of the shift between glucose and fatty acid utilization in cells (favoring fatty acid utilization) was shown to be important for supporting intracellular T. cruzi growth. This is intriguing given that T. cruzi exhibit tropism in vivo for muscle cells that are biased toward fatt acid utilization. While many of the tools exist to study metabolism in mammalian cells, these tools have yet to be applied to the study of host cell metabolism in the context of T. cruzi infection. Thus, the aim of this exploratory R21 proposal is to establish an experimental framework with methodologies and tools developed primarily for studies of metabolic disease (diabetes, cancer etc) that will allow us to determine the extent to which host cell metabolism is altered in T. cruzi-infected host cells and how this impacts intracellular parasite growth. Understanding the intimate relationship between host metabolism and T. cruzi amastigote growth will provide a critical piece of biology that is currently lacking in our knowledge of T. cruzi-host interactions and will help to elucidate novel targets for the control of T. cruzi growth